(a) Field of the Invention
The present invention relates to an improved structure of a brake-tuning device for a bicycle, and in particular, relates to a tuning device for the brake of a bicycle by having an adjusting bolt to regulate the distance between the brake arm and the wheel frame so that the braking operation is effective.
(b) Description of the Prior Art
FIGS. 1 to 3 show the structure of a conventional brake-tuning device comprising a braking arm 1, an annular rim 6 mounted onto the braking arm 1, a locking seat 7 having an adjusting bolt 71 positioned on one lateral side thereof, an adjusting block 8 mounted within the locking seat 7 with one end urging against the adjusting bolt 71, and a spring 91 having one end mounted to the adjusting block 8 and the other end mounted to an insert 9. When the braking arm 1 is not balanced in the process of braking, the adjusting bolt 71 can be adjusted by rotating the bolt 71 clockwise (inward) such that the bolt 71 urges the adjusting block 8 and drives the spring 91 to deform. Thus, the distance between the braking arm 1 and the wheel frame is adjusted to provide an effective braking operation. However, the conventional brake-tuning structure has the following drawbacks:
1. Adjustment of brake is not precise
In the conventional brake tuning, the annular rim 6, the locking seat 7 and the adjusting block 8 are involved in order to proceed with the fine adjustment of the brake (as shown in FIG. 3A). However, as these parts are not so precisely made during the manufacturing process, therefore, it is not possible to achieve precise fine tuning of brake. Furthermore, if the adjusting block 8 is biased towards the locking position of the adjusting bolt 71, the alignment of the adjusting block 8 with the adjusting bolt 71 cannot be obtained (refer to FIG. 3B). When the guarding edge 72 of the adjusting block 8 is too long, the adjusting block 8 cannot be accurately urged against (refer to 3C). In another situation, when the annular rim 6 is too thin and the adjusting block 8 protruded beyond the locking seat 7, the adjusting of the bolt 71 does not urge the adjusting block 8 (refer to FIG. 3D) and the brake-tuning cannot be achieved.
2. High cost in combination of parts:
As the conventional brake tuning involves a plurality of parts, the combination of these parts are too complicated and it causes problem in the storage of these parts.
3. Inconvenient for subsequent brake tuning
As the container 92 for these parts is discarded after the first adjustment of the brake, if subsequent brake tuning is needed, these parts shall be scattered everywhere. Thus, the final installation of these part may be not convenient.